This application is related to concurrently filed and co-pending application Ser. No. 07/916,754.
The subject invention relates to arrangements for rapidly interrupting DC load current in a power line interconnecting a source of electric energy and a load and, particularly, for rapidly opening circuit breaking devices without significant arcing.
When DC load currents of substantial magnitude are interrupted by interrupting devices, such as circuit breakers or switches, the arc produced across the opening contacts of the interruption device prohibits interruption until the arc voltage drop is made to exceed the DC source voltage, or until the arc is de-ionized by diverting arc current to a parallel path for a time sufficient for de-ionization and recovery of breakdown voltage at least equal to the source voltage. Arc energy erodes the metallic contacts, erodes and deposits conductive material on insulator surfaces in the vicinity, emits contaminants to the atmosphere, and delays completion of current interruption by the time required for de-ionization and recovery of breakdown voltage. Thus, the reduction of arc energy, particularly its elimination, can provide significantly faster interruption of DC current, with smaller contacts and insulators, and with higher reliability.
Applicant's U.S. Pat. No. 4,636,907 entitled "Arcless Circuit Interrupter", which is assigned to the assignee of the subject application and is herein incorporated by reference, discloses an arrangement for diverting load current, prior to opening of the interruption device, to a parallel current interrupter circuit, thereby essentially eliminating the arc. It discloses a controlled impedance circuit in series with the interruption device. Responsive to the interruption signal, the impedance value is stepped up from a low value to produce a sufficient voltage drop to fully divert the load current prior to the opening of the interruption device. Applicant's U.S. Pat. No. 4,658,227 entitled "High Speed Magnetic Contact Driver", which is also assigned to the assignee of the subject application and is herein incorporated by reference, discloses an interruption device having exceptionally fast and predictable opening of the contacts. Applicant's U.S. Pat. No. 4,723,187 entitled "Current Commutation Circuit", which is also assigned to the assignee of the subject application and is herein incorporated by reference, discloses a current interrupter circuit having exceptionally low initial impedance which enables very rapid transfer of current from the interrupting device, and further teaches the use of the series controlled impedance and the high speed contact driver in combination. This combination has been found to provide very fast current interruption in both AC and DC applications. However, for strictly DC uses, wherein the direction of current flow and voltage polarity is fixed, certain simplifications can be made which both improve performance and reduce the cost and complexity of the interrupter.